There are machined cages for a cylindrical roller bearing of an integral type or a split type. The machined cage of the split type should be called a two-bodied rivet-type machined cage. As shown in FIGS. 11A, 11B, and 12, a main body 12 and a side plate 14 are connected by rivets 16 (see paragraph 0002 and FIG. 14 of JP 2001-12477 A). The main body 12 is composed of a disk-like side plate portion 18 and a plurality of column portions 20 axially protruding from the side plate portion 18. Each of the column portions 20 has a rivet hole 24 passing therethrough in the axial direction of the main body 12. The side plate 14 has a disk shape as with the side plate portion 18 of the main body 12 and is provided with rivet holes 26 at the same intervals as the rivet holes 24 of the main body 18. The side plate 14 is caused to abut on a front end of the column portion 20 of the main body 18, the rivets 16 are inserted into the rivet holes 24 of the main body 18 and the rivet holes 26 of the side plate 14, and ends of those are swaged, thereby connecting the main body 12 and the side plate 14. The column portions 20 are arranged at equal intervals in the circumferential direction. Between the adjacent column portions 20, pockets 22 are defined. One of a pair of surfaces of wall surfaces defining the pocket 22, opposing each other in an axial direction is formed by the side plate portion 18 and the other of those is formed by the side plate 14. Further, a pair of surfaces of the wall surfaces defining the pocket 22, opposing each other in a circumferential direction is formed by the side surfaces of the column 20.
As shown in FIGS. 13A, 13B, and 14, in the integral machined cage, a square hole is cut in a ring-like material, thereby forming a pair of side plates 32 and 34 and a plurality of columns 36 and pockets 38 are defined between the adjacent columns 36 (see FIGS. 1 and 2 of JP 11-218135 A). Reliefs 40 are formed at four corners of each of the pockets 38. As understood from FIG. 14, side surfaces of the column 36 have circular arc sections. Note that, as described in JP 11-218135 A, even if a surface for guiding the cylindrical roller has a circular arc shape, there are some cases where the reliefs are not formed. A basic method of machining the pockets of the former cage is basically drilling and end mill machining, and that of the latter cage is a machining method disclosed in JP 2001-191214 A.
Further, there is also an integral cage disclosed in Japanese Utility Model Application Laid-open No. Hei 5-12753, in which the side surfaces of the pockets are in parallel to each other. The machining method in this case is assumed to be broaching considering that the reliefs are not formed at the four corners of each pocket.    Patent Document 1: JP 11-218135 A (FIGS. 1, 2, and 4)    Patent Document 2: JP 2001-12477 A (paragraph numbers 0002, 0031, and FIGS. 6, 8, and 14)    Patent Document 3: Japanese Utility Model Application Laid-open No. Hei 5-12753 (paragraph number 0010)